1. Field of the Invention
This invention relates generally to tool couple elements and in particular to those attached to a vise for holding a threading die in contact with a workpiece while the die is used to thread the end of the workpiece.
2. Description of the Prior Art
The cutting of the initial thread on a pipe in a manual operation requires the operator to push the die onto the pipe while simultaneously turning the die handle. This operation is at times a very difficult and awkward task because a large amount of pressure must, on occasion, be exerted on the die against the pipe in order to cut the initial threads. Moreover, if the initial attempt to form a thread is unsuccessful, the operator usually finds that successive attempts are also unsuccessful; the die merely continues to cut a steep chamfer or bevel on the leading edge of the pipe.
To remedy such a situation, those operators fortunate enough to have a grinding wheel close at hand fashion a slight taper on the outer surface of the pipe so that the cutting edges behind the anterior cutting edge of the die, as well as the latter edge, are engaged in the initial cutting action. However, the operation of shaping a taper is time-consuming and often impractical.
Too frequently, frustrated operators resort to hammering a die onto the end of a pipe in order to start the die. Such hammering usually destroys an expensive tool, the threading die.
The awkwardness of the process of trying to press the die inward and to rotate the die handle simultaneously is further compounded when one attempts to thread the end of an installed pipe. In the past, most operators have elected to wrench out the section of pipe which must be cut and re-threaded and to work on that section in a place where the pipe can be secured close to the end to be threaded. The pipe-fitting activity associated with removing the entire pipe section can be time-consuming and costly, especially when the joint connecting the pipe section to other pipe is relatively inaccessible or the threads of the joint have become chemically bonded to one another by rusting or other chemical action.